On 1/24/23 12:34, Jason Gunthorpe wrote:
Move the flags that should not/are not used outside gup.c and related into
mm/internal.h to discourage driver abuse.
To make this more maintainable going forward compact the two FOLL ranges
with new bit numbers from 0 to 11 and 16 to 21, using shifts so it is
explict.
Switch to an enum so the whole thing is easier to read.
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
---
include/linux/mm_types.h | 57 ++++++++++++++++++++++++----------------
mm/internal.h | 15 +++++++++++
2 files changed, 50 insertions(+), 22 deletions(-)
Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
thanks,
--
John Hubbard
NVIDIA
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 518617431f8085..dbfc3a7e9559b4 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -1039,9 +1039,6 @@ typedef unsigned int __bitwise zap_flags_t;
* FOLL_PIN and FOLL_LONGTERM may be used in various combinations with each
* other. Here is what they mean, and how to use them:
*
- * FOLL_LONGTERM indicates that the page will be held for an indefinite time
- * period _often_ under userspace control. This is in contrast to
- * iov_iter_get_pages(), whose usages are transient.
*
* FIXME: For pages which are part of a filesystem, mappings are subject to the
* lifetime enforced by the filesystem and we need guarantees that longterm
@@ -1085,24 +1082,40 @@ typedef unsigned int __bitwise zap_flags_t;
* Please see Documentation/core-api/pin_user_pages.rst for more information.
*/
-#define FOLL_WRITE 0x01 /* check pte is writable */
-#define FOLL_TOUCH 0x02 /* mark page accessed */
-#define FOLL_GET 0x04 /* do get_page on page */
-#define FOLL_DUMP 0x08 /* give error on hole if it would be zero */
-#define FOLL_FORCE 0x10 /* get_user_pages read/write w/o permission */
-#define FOLL_NOWAIT 0x20 /* if a disk transfer is needed, start the IO
- * and return without waiting upon it */
-#define FOLL_NOFAULT 0x80 /* do not fault in pages */
-#define FOLL_HWPOISON 0x100 /* check page is hwpoisoned */
-#define FOLL_TRIED 0x800 /* a retry, previous pass started an IO */
-#define FOLL_REMOTE 0x2000 /* we are working on non-current tsk/mm */
-#define FOLL_ANON 0x8000 /* don't do file mappings */
-#define FOLL_LONGTERM 0x10000 /* mapping lifetime is indefinite: see below */
-#define FOLL_SPLIT_PMD 0x20000 /* split huge pmd before returning */
-#define FOLL_PIN 0x40000 /* pages must be released via unpin_user_page */
-#define FOLL_FAST_ONLY 0x80000 /* gup_fast: prevent fall-back to slow gup */
-#define FOLL_PCI_P2PDMA 0x100000 /* allow returning PCI P2PDMA pages */
-#define FOLL_INTERRUPTIBLE 0x200000 /* allow interrupts from generic signals */
-#define FOLL_UNLOCKABLE 0x400000 /* allow unlocking the mmap lock (internal only) */
+enum {
+ /* check pte is writable */
+ FOLL_WRITE = 1 << 0,
+ /* do get_page on page */
+ FOLL_GET = 1 << 1,
+ /* give error on hole if it would be zero */
+ FOLL_DUMP = 1 << 2,
+ /* get_user_pages read/write w/o permission */
+ FOLL_FORCE = 1 << 3,
+ /*
+ * if a disk transfer is needed, start the IO and return without waiting
+ * upon it
+ */
+ FOLL_NOWAIT = 1 << 4,
+ /* do not fault in pages */
+ FOLL_NOFAULT = 1 << 5,
+ /* check page is hwpoisoned */
+ FOLL_HWPOISON = 1 << 6,
+ /* don't do file mappings */
+ FOLL_ANON = 1 << 7,
+ /*
+ * FOLL_LONGTERM indicates that the page will be held for an indefinite
+ * time period _often_ under userspace control. This is in contrast to
+ * iov_iter_get_pages(), whose usages are transient.
+ */
+ FOLL_LONGTERM = 1 << 8,
+ /* split huge pmd before returning */
+ FOLL_SPLIT_PMD = 1 << 9,
+ /* allow returning PCI P2PDMA pages */
+ FOLL_PCI_P2PDMA = 1 << 10,
+ /* allow interrupts from generic signals */
+ FOLL_INTERRUPTIBLE = 1 << 11,
+
+ /* See also internal only FOLL flags in mm/internal.h */
+};
#endif /* _LINUX_MM_TYPES_H */
diff --git a/mm/internal.h b/mm/internal.h
index 5c1310b98db64d..673b4b1d5f4c79 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -854,6 +854,21 @@ int migrate_device_coherent_page(struct page *page);
struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags);
int __must_check try_grab_page(struct page *page, unsigned int flags);
+enum {
+ /* mark page accessed */
+ FOLL_TOUCH = 1 << 16,
+ /* a retry, previous pass started an IO */
+ FOLL_TRIED = 1 << 17,
+ /* we are working on non-current tsk/mm */
+ FOLL_REMOTE = 1 << 18,
+ /* pages must be released via unpin_user_page */
+ FOLL_PIN = 1 << 19,
+ /* gup_fast: prevent fall-back to slow gup */
+ FOLL_FAST_ONLY = 1 << 20,
+ /* allow unlocking the mmap lock */
+ FOLL_UNLOCKABLE = 1 << 21,
+};
+
/*
* Indicates for which pages that are write-protected in the page table,
* whether GUP has to trigger unsharing via FAULT_FLAG_UNSHARE such that the
